1. Field of the Invention
This invention relates to a photogrammetric plotting apparatus for the stereoscopic plotting of photograms, and more particularly to a photogrammetric plotting apparatus which is particularly useful for the revisioning of maps.
2. Prior Art
Photogrammetry is the science or art of utilizing stereo perception to obtain reliable measurements of elevation and position of terrain from a pair of stereoscopically related photograms, e.g. aerial photographs. From these photograms typographic and planimetric maps are prepared by what is known as photogrammetric stereo plotting. Photogrammetric principles are also utilized in numerous fields to solve problems of mensuration requiring both absolute and relative determinations of size, shape, depth, height and location of objects in their environment; archeology, livestock evaluation, medical examinations, are but a few such fields of use. The utility of this invention is not to be considered limited only to map making usage, as described herein, but such use is only exemplary.
Generally, two aerial photographs, i.e. photograms, of the same terrain are taken at different points in the same vertical plane. The photograms are then compared to obtain points of equal elevation. A characteristic of true vertical stereophotograms is that all points at a given elevation on one photogram will "coincide" exactly with the same points on a second photogram. When these constant elevation points merge to form a random type curve, the curve is called a contour line. Thus, if the two stereoscopically related photograms are placed one above the other the contour lines for a given elevation could be made to lie exctly in coincidence by displacing in a horizontal plane one photogram relative to the other. For each elevation there is a corresponding displacement at which the lines at that elevation coincide. By following these lines with exploring motions relative to the photograms, whether manually or automatically, contour lines of equal evaluation can be traced.
Numerous complex systems have been devised to aid the operator in plotting such terrain and relief maps. These systems are generally known as photogrammetric plotting apparatus or stereo restitution instruments and are used for the production and revision of topographic maps. These systems require high accuracy and versatility.
Such photogrammetric plotting apparatus are well known in the art. See for example the following U.S. patents:
U.S. Pat. No. 2,910,910 to Rosenfeld et al; PA1 U.S. Pat. No. 2,912,761 to Woodward et al; PA1 U.S. Pat. No. 2,933,008 to Barnett I; PA1 U.S. Pat. No. 4,988,953 to Barnett II; PA1 U.S. Pat. No. 3,004,464 to Leighton et al; PA1 U.S. Pat. No. 3,170,238 to Yzerman; PA1 U.S. Pat. No. 3,267,286 to Bailey et al; PA1 U.S. Pat. No. 3,355,807 to Schoeler et al; PA1 U.S. Pat. No. 3,465,444 to Blachut et al; PA1 U.S. Pat. No. 3,678,582 to Helava et al; PA1 U.S. Pat. No. 3,989,933 to Inghilleri; PA1 U.S. Pat. No. 4,005,932 to Gates; and PA1 U.S. Pat. No. 3,057,336 to Malinge. PA1 (a) an optical system means for the operator viewing an image of a stereo model derived from a pair of stereoscopically related photograms; PA1 (b) an operator controlled means for effecting stereomodel exploring motions relative to the photograms; PA1 (c) a tracing or display device; PA1 (d) a means for converting the exploring motions into plotting motions for the tracing or display device. PA1 The KERN PG 3 System uses a closed circuit television system for closeup vision around the pencil on the drawing table. The television camera is mounted on the drafting head of the plotter of the drawing table and the television monitor is on the side of the operator. PA1 (a) an optical system means for operator viewing of an image of a first stereomodel derived from a pair of stereoscopically related photograms; PA1 (b) operator controlled means for effecting stereomodel exploring motions relative to the photograms; PA1 (c) a tracing or display device; PA1 (d) means for converting the exploring motions into plotting motions for the tracing or display device; PA1 (e) means for scanning image data of a second model to produce an image of the second model; PA1 (d) means for conveying the image of the second model to the optical system; PA1 wherein the optical system includes a means for superimposing the image of the second model on the image of the first stereomodel for simultaneous viewing by the operator.
The entire disclosures of all these U.S. patents are incorporated herein by reference.
Known photogrammetric apparatus are the KERN PG 2, PG 2-AT, PG 3 and PG 2-SSL systems sold by Kern Instruments, Inc. Brewster, N.Y. The aforementioned Yzerman patent and Swiss Pat. Nos. 372,849, 375,913, 443,702, 480,650, 527,383 and 531,704 describe methods and apparatus used in these systems. The entire disclosure of all of these Swiss Patents are incorporated herein by reference.
Generally, such a prior art photogrammetric plotting apparatus comprises:
Such an apparatus is exemplified in the aforementioned Rosenfeld et al, Woodward et al, Leighton et al, Blachut et al, Helava et al, Inghilleri, Gates and Malinge references and the KERN systems.
In the revisioning of maps, generally an existing map is displayed on the tracing or display device, typically an automatic tracing table, and recent aerial photographs or photograms of the same land area are placed in the photogrammetric plotting apparatus and viewed through the optical system means. The operator must constantly switch his viewing field from the existing map to the new photograms in the apparatus to determine what features are in the photograms which are not in the existing map and vis-a-versa. There is apparently no known photogrammetric plotting system or apparatus which permits the simultaneous viewing of the existing map and the new aerial photograms simultaneously.
Systems and apparatus have been used which utilize television cameras and monitors, for example:
Rosenfeld et al utilizes a television scanning unit to scan a stereomodel produced by a pair of stereoscopic photograms. The information from the scanning unit is sent to an electronic computing mechanism which determines if the scanned spot is or is not on the surface of the stereomodel. If the spot is determined to be on the surface, the apparatus marks ines of successive dots on a sheet to correspond to these spots.
Woodward et al utilizes two photoelectric scanners to scan images produced by the projection of copies of the original photographs. The photoelectric scanners convert the optical patterns into electrical signals which after amplification and certain comparisons may then be used to provide marks on the mapping surface.
Barnett I and Barnett II--photographs or negatives taken through aerial photography are presented to two television cameras. The camera signals are controlled and viewed on their separate control monitors and then mixed together in the master monitor. The images on the master monitor may then be photographed with a camera. Optionally the signals from the signal switching amplifier may be stored in a magnetic memory unit for subsequent use, such as transferring it to the television monitor.
Leighton et al uses a photoelectric scanning process which includes a vidicon camera for scanning a stereomodel over a plane surface produced by a set of stereo dispositives.
Gates--a television camera projects an image of a flexible platen onto a screen. Information from the screen is then traced on an overlay.
Malinge provides a screen which has images of the photograms projected thereon, and is observed by the operator when he looks through the analyzer. Malinge is significant in that it requires the observer to be approximately the same distance from the screen as from the useful region of the tracing or display device so that the observer can easily and without fatigue watch the screen and then watch the plotting device without having to refocus his eyes to any substantial extent.
Additionally, the ZOOM TRANSFER SCOPE of Bausch and Lomb, enables the operator to view two separate images simultaneously. This system however does not relate to stereo photogrammetric plotting and does not produce an overlay with a television camera or monitor.